Fluid drive mechanism

Abstract

A mechanism for moving an element in opposite directions includes a piston connected with the element. The piston reciprocates in a cylinder as high pressure fluid is alternately directed against one side or the other of the piston by a rotatable directional valve. The directional valve is rotated by a gerotor motor. A single rotatable valve element has passages at one end which form a commutator valve for the gerotor motor and ports at the other end which form the directional valve. A passage through the valve element connects the output of the gerotor motor with the directional valve ports. Cushioning means are provided to damp the motion of the piston at each end of its stroke to prevent impact with the ends of the cylinder.

Having described a specific preferred embodiment of the invention, the following is claimed: 
     
       1. A mechanism for moving an element in opposite directions, said mechanism comprising fluid motor means including at least one piston member and one cylinder member defining first and second expansible chambers, said piston member and cylinder member moving in one direction relative to each other when the first chamber is expanded and moving in the opposite direction relative to each other when the second chamber is expanded,   a valve element having a high pressure port through which fluid is directed to the chamber that expands and a low pressure port through which fluid is directed from the chamber that contracts,   a fluid motor operatively connected to said valve element for moving said valve element to alternately communicate said high and low pressure ports with said first and second expansible chambers upon movement of said valve element to effect relative movement of said piston member and cylinder member in opposite directions, said fluid motor having a fluid inlet for communication with a fluid source and a fluid outlet, and   means defining a fluid conduit for communicating said fluid outlet with said high pressure port of said valve element.   
     
     
       2. A mechanism as set forth in claim 1 wherein said fluid motor for moving said valve element is a gerotor motor. 
     
     
       3. A mechanism as set forth in claim 2 wherein said gerotor motor includes an internally toothed gear and an externally toothed gear, said gears being disposed for relative orbital and rotary movement, and means for connecting one of said gears with said valve element to effect movement of said valve element. 
     
     
       4. A mechanism as set forth in claim 3 wherein said valve element is rotatable and said fluid motor is effective to rotate said valve element. 
     
     
       5. A mechanism as set forth in claim 1 further including cushioning means for dampening relative movement of said piston and cylinder after said piston and cylinder have started relative movement in one direction and before said piston and cylinder reverse their direction of relative movement. 
     
     
       6. A mechanism as set forth in claim 5 wherein said cushioning means includes means for gradually reducing the rate of flow through said low pressure port from the contracting one of said expansible chambers after said piston and cylinder have started relative movement in one direction and prior to their reversing of their direction of relative movement. 
     
     
       7. A mechanism for effecting reciprocating movement of an output element, said mechanism comprising at least one piston and cylinder for moving said element and defining first and second expansible chambers,   a valve element,   said valve element having first and second pressure ports and being rotatable to alternately communicate said first and second ports with said first and second chambers,   a rotary fluid motor having a rotatable output member, and   means for transmitting rotary movement of said output member to said valve element to rotate said valve element, said means for transmitting rotary movement comprising a drive link between said output member and said valve element.   
     
     
       8. A mechanism as set forth in claim 7 wherein said first and second pressure ports comprise high and low pressure ports, said rotary motor including a fluid inlet and an outlet, and said mechanism further includes means for communicating fluid from said outlet to said high pressure port of said valve element. 
     
     
       9. A mechanism as set forth in claim 8 wherein said fluid motor is a gerotor motor having a manifold plate, a commutator valve disposed in abutting engagement with said manifold plate, said commutator valve including first and second sets of passages formed in said valve element and communicating sequentially with said passages in said manifold plate as said valve element rotates. 
     
     
       10. A mechanism as set forth in claim 9 wherein said first and second sets of passages in said valve element and said high and low pressure ports in said valve element are disposed in opposite end portions of said valve element. 
     
     
       11. A mechanism for effecting movement of an element in opposite directions, said mechanism comprising (a) a gerotor motor including an internally toothed gear member and an externally toothed gear member located eccentrically within said internally toothed gear member and having one less tooth than said internally toothed gear member, said gear members having relative rotatable and orbital movement, the teeth of said rotor and stator defining expansible and contractible fluid pockets, and   commutator valve means for directing high pressure fluid to the fluid pockets as they are expanding to effect relative rotation of the gear members and for directing high pressure fluid from the pockets as they are contracting,     (b) an expansible chamber fluid motor connected with said element and having a piston and cylinder defining a pair of expansible chambers,   (c) directional valve means movable to alternately (i) deliver high pressure fluid from the commutator valve means to one of said pair of expansible chambers and permit fluid to flow out of the other of said pair of expansible chambers and (ii) deliver high pressure fluid from the commutator valve means to the other of said pair of expansible chambers and permit fluid to flow out of the one chamber thereby effecting movement of said element in opposite directions, and   (d) means connecting one of said gear members with said directional valve means to effect said movement of said directional valve means in timed relation to at least one of said relative movements of said gear members.   
     
     
       12. A mechanism as set forth in claim 11 wherein said internally toothed gear is fixed and said externally toothed gear rotates and orbits relative to said internally toothed gear, and said means connecting one of said gear members with said directional valve comprises a drive link connecting said externally toothed gear to said directional valve to rotate said directional valve upon rotation of said externally toothed gear. 
     
     
       13. A mechanism as set forth in claim 12 wherein said commutator valve means includes first and second sets of passages formed in a first end portion of a valve element and said directional valve means includes a high pressure port and a low pressure port formed in a second end portion of said valve element opposite from said first end portion. 
     
     
       14. A mechanism as set forth in claim 13 wherein said valve element includes first and second parallel end faces and is rotatable about an axis normal to said end faces, said high and low pressure ports forming openings in said second end face, and wherein said mechanism further comprises housing means having a surface abutting said second end face, first and second passage means in said housing means for communicating fluid from said surface to said expansible chambers, each of said first and second passage means including an opening in said surface. 
     
     
       15. A mechanism as set forth in claim 14 wherein the gerotor motor further includes a manifold plate disposed in abutting engagement with said first end surface of said valve element, said manifold plate having a plurality of passages therethrough each of which communicates with one of said expansible and contractible fluid pockets in said gerotor motor, and passage means connecting one of said sets of passages of said commutator valve means in said first end portion of said valve element with said high pressure port in said second end portion of said valve element.